The present invention relates generally to an imaging system, and more particularly to an X-ray mammogram tomosynthesis system.
Conventional X-ray mammography imaging systems utilize an X-ray source mounted on a supporting frame. The frame is manually rotated by the system operator to a place the X-ray source into desired position adjacent to a patient's breast. The X-ray source emits a first shot of X-rays through the patient's breast and an image is captured on a first an X-ray sensitive film positioned on the opposite side of the patient's breast. The frame is then manually rotated into another position by the operator and a second X-ray sensitive film is exposed by a second shot of X-rays. This procedure can be repeated several times to generate several images on different films. The images on the X-ray sensitive films may then be evaluated by a physician and/or digitized and evaluated by a computer. However, such a system produces a two dimensional image of the patient's breast, which provides insufficient information about the presence of tumors and calcification and often leads to false positive readings.
U.S. Pat. No 5,872,828 discloses a tomosynthesis system for breast imaging. This system produces a three dimensional image of the breast being imaged. The tomosynthesis system contains an X-ray source which moves in an arc shaped path over the breast that is being imaged, a stationary digital X-ray detector and an image processor. The detector is mounted on a stationary portion of a support structure. The X-ray source is mounted on a movable portion of the support structure. The movable portion of the support structure is an arm whose lower end is rotatably attached to the stationary support structure at a pivot point, and whose upper end supports the X-ray source.
However, this tomosynthesis system suffers from several disadvantages. First, the X-ray source is subject to a high amount of vibration because it is mounted to the free, upper end of a rotating arm, while the arm is supported only at the pivot point at its lower end. The vibration of the X-ray source distorts the image. Second, this system requires a high amount of driving power to move the X-ray source. The high driving power is required because torque is applied to the fixed, lower end of the arm, while the heavy X-ray source is mounted to the free, upper end of the arm.